The present invention relates to implantable medical devices for delivering a liquid therapeutic substance to a delivery site within a patient. More particularly, it relates to systems and methods for guiding a hypodermic needle tip toward a septum opening associated with an implantable therapeutic substance delivery device.
A variety of implantable medical devices are available for treating patients. For example, implantable therapeutic substance delivery devices are typically used to deliver infusion media or therapeutic substance (such as medication) to a patient at a regulated dosage. The implantable therapeutic substance delivery device (sometimes referred to as a drug pump or medicament pump) is implanted by a clinician into a patient at a location appropriate for the therapy. Typically, an infusion catheter is connected to an outlet of the device and is implanted/positioned to infuse the therapeutic substance at the desired therapy site so as to treat a condition such as pain, spasticity, cancer, neurodegenerative disease, trauma, or other medical condition. The term “implantable therapeutic substance delivery device” as used herein, refers to any device for delivering medicaments including, but not limited to, bladder pumps, accumulator pumps, fixed-rate bellows pumps, and the like, as well as implantable delivery devices that do not include a pump.
In general terms, the implantable therapeutic substance delivery device commonly includes a drug reservoir containing a volume of the infusion media along with a pumping and/or metering mechanism to propel the infusion media in some metered or constant flow dosage to the desired location from the reservoir via the catheter. Over time, the reservoir becomes depleted and it is necessary to refill the device with a new supply of the therapeutic substance. In order to avoid the need for surgery to access and refill the device, it is desirable to have the ability to percutaneously refill the drug reservoir. This is commonly achieved by providing the delivery device with a reservoir refill port that otherwise includes a resilient, resealable septum. The refill port is percutaneously accessible by introducing a hypodermic needle through the skin and into the refill port, and then through the septum, thereby forming a fluid connection between the needle and the drug reservoir. Additional septum-type ports can also be provided, such as a catheter access port. The catheter access port is also accessible percutaneously via hypodermic needle, and provides direct access to the catheter, bypassing the pumping/metering mechanism to allow the infusion of media directly into the patient, or removal of fluid from the patient (e.g., cerebral spinal fluid), via the catheter.
Percutaneously accessing the septum with a hypodermic needle can be difficult. One well-accepted approach entails the clinician using his/her fingers to palpate the device's periphery through the patient's skin. Once generally located, the clinician then searches/palpates for the desired port, again using his/her fingers. Port location relative to a perimeter or outline of the device is normally generally known to the clinician, as he or she will have a working understanding of the device's footprint and port location(s) relative thereto. In this regard, a template can be employed that can otherwise provide an external visual map of port location when properly arranged on the patient's skin. In general terms, once the device's general location and orientation is ascertained, the template is placed onto the patient's skin in general alignment with the estimated implanted device location and orientation. The template includes a representation of the port location(s), thus giving the clinician visual guidance.
Regardless of how the clinician initially estimates port location, a hypodermic needle is then pierced through the patient's skin. While the clinician's initial estimate of the port location is in many instances correct, on occasion the hypodermic needle may not impinge directly into the port/septum. For example, where the patient's skin is relatively thick, it may be difficult for the clinician to accurately estimate port location and/or the clinician may simply be offline from the anticipated target. Regardless, where the hypodermic needle does not immediately enter the port with initial insertion, the clinician will tactilely sense a hard stop to forward movement of the hypodermic needle (i.e., as the needle tip contacts the rigid housing of the device) as compared to a more subtle resistance to needle advancement when piercing through the septum.
Upon determining that the hypodermic needle is not within the port, the clinician can remove the needle and then make another insertion attempt. In many instances, however, the clinician will be of the mind set that his/her initial estimate of the port/septum location is approximately correct, that the needle was introduced in-line with this estimation, and thus that the needle tip must be in close proximity to the actual port opening. As a result, instead of removing the needle and re-attempting the percutaneous insertion, the clinician will oftentimes drag the needle tip along the contacted face of the device, searching for the port opening. While viable, this technique can be time consuming as the clinician may inadvertently move the needle tip in a direction that is actually away from the port opening, and can be source of discomfort for the patient.
In light of the above, some efforts have been made to enhance the clinician's ability to better estimate port location prior to piercing the needle through the patient's skin. The above-described device template is one example. Other, more complex devices have also been suggested, such as electronically sensing the port opening location, employing sensors that detect the presence of the needle relative to a port opening, etc. While potentially viable, these techniques entail additional costs and clinician training. Further, even with these devices in place, the opportunity for misalignment of the needle tip relative to the port opening with initial insertion still remains.
In light of the above, a need exists for a system and method for guiding a misaligned needle tip toward a septum port associated with an implantable therapeutic substance delivery device.